Actuator may be, prima facie, a part of the valve with which it is used, but actuators for valves, imported / exported separately are not provided in the valve heading 8481. Actuator is a gear assembly and is more specifically provided in heading 8483.
Actuator, when presented separately, is 8483.40.5010 HTSUS or 8483.40.4010 Schedule B, which provides for fixed ratio speed changers
Source: N025719
